Partial support is requested for the 12th International Symposium on the Chemistry and Biology of Pteridines and Folates, to be held June 17-22, 2001, at the Natcher Center, NIH, Bethesda, MD. This conference offers a unique opportunity for clinician scientists and basic scientists from a broad group of disciplines, who share an interest in folate and pteridine research, to interact both formally and informally. Funds are requested to defray travel costs of graduate students, residents and postdoctoral fellows and young investigators, and some plenary speakers. A preliminary program is presented which includes well-established scientists and junior scientists just entering the field. In addition, topics scan the entire spectrum from current clinical problems to areas of the most sophisticated biochemical and biophysical research. Sessions have been scheduled on clinical disorders of pteridine and folate metabolism, including genetic and metabolic aspects. Sessions include the role of pteridines in endothelial function, nitric oxide synthase, and aromatic amino acid hydroxylases, and the relationship of folate and homocysteine to vascular disease and neural tube defects. Other sessions involve the control of biosynthesis of these cofactors, the chemistry of folates and pteridines, the role of molybdopterins, and the regulation of one carbon metabolism and methionine synthesis. Additional sessions cover adenosylmethionine and methyl group transfer reactions as well as emerging targets for new chemotherapeutic agents against malignant diseases. In addition to these formal presentations, the program will be complemented with poster sessions and workshops. These offer many opportunities for informal discussions and allow graduate students, residents and postdoctoral fellows, as well as established scientists, an opportunity to present and discuss their work. As in the past, the new research presented at the symposium will be disseminated to a much wider audience in the form of a symposium book. A broad range of speakers and participants will be sought for the 2001 Symposium, particularly graduate and postgraduate students, women and minorities.